Using @ts-expect-error in a @ts-nocheck file

[nicojs]

TypeScript Version: 3.9 - 4.0.0-beta, v4.0.0-dev.20200705

Search Terms: "ts-nocheck ts-expect-error" "ts-expect-error"

Code

// @ts-nocheck
// @ts-expect-error
'a' - 'b'

Expected behavior: No compile error

Actual behavior: Error: Unused '@ts-expect-error' directive.(2578)

Playground Link: https://www.typescriptlang.org/play?ts=4.0.0-beta#code/PTAEAEBcGcFoDsD2BjAFgU2QawFAgjLOgB4AOmkRATlYlTgOQCGDosoDARg0A

Related Issues:

[RyanCavanaugh]

[JoshuaKGoldberg]

What direction does this bug point @RyanCavanaugh? I would think that the code is behaving as expected: the // @ts-expect-error is redundant and shouldn't exist. Perhaps a more specific error message?

Error: Unused '@ts-expect-error' directive because of an earlier '@ts-no-check' directive.
  '@ts-no-check' was specified here: ...

Per the comments in stryker-mutator/stryker-js#2403 (comment) I think the right resolution would be for fancy code mutation services to strip out comments. cc @nicojs, since it looks like you already implemented that in stryker-mutator/stryker-js#2365, right?

edit: my comment double-posted; I deleted the second one...

[RyanCavanaugh]

I think nocheck is the higher-order bit here; the intent of that is to "shut up for the whole file" and that should include expect-error not issuing an error.

[JoshuaKGoldberg]

This actually doesn't give an error anymore in 4.1.5 and up: original example; example with code between the two comments. 🤷

[RyanCavanaugh]

Must have been fixed elsewhere then.